This invention relates generally to polyester processes and apparatuses, more specifically, to polyester processes and apparatuses comprising an adsorption system in the absence of a water column and other distillation system components.
As the business of manufacturing polyesters becomes more competitive, alternative lower cost manufacturing processes and apparatuses have become highly desirable. A variety of processes and apparatuses have been developed, however, these systems contain complex and costly designs that cannot be built or installed quickly. They also require costly expertise to properly maintain and operate. For example, in typical polyester processing facilities, it is common for a reactor system to contain a series of distillation columns, for among various purposes, recovering unreacted dihydroxy compounds that may be contained in the various fluid streams that result from the polyester manufacturing processes.
A typical distillation system would comprise a water column, stripper column, and an MGM column (mixed glycol and monomer column or ethylene glycol condensate column). Commonly, fluid streams from one or more reactors are sent to the water column. There, water is separated from the glycol or other dihydroxy compound. Low boilers, such as water, are removed at the top of the column and sent to the stripper column, and the dihydroxy compounds such as glycol and other high boilers are removed at the bottom of the column where they can be sent back to the reactor system or, alternatively, sent to a storage facility. The stripper column separates out at the top of the stripper column various components, such as paradioxane, that cannot be sent to a waste water treatment facility.
These are complex and costly unit operations which further require significant amounts of space for proper installation and operation. Therefore, there is a need in the art for lower cost, simpler apparatuses and processes for separating and recovering unreacted dihydroxy compounds from the fluid streams that can result from a polyester manufacturing process.
Among other aspects, the present invention provides a process and apparatus for separating and recovering a dihydroxy compound from fluid streams that result from a polyester manufacturing process. More specifically, the invention provides for the use of an adsorption system in the absence of a water column and other distillation devices to provide a more compact and cost effective means for recovering a dihydroxy compound. As such, the use of an adsorption system according to the present invention in a polyester manufacturing process can reduce or even eliminate the need for bulky columns, equipment, tanks, agitators, pumps, and the like.
Therefore, in a first aspect, the present invention provides a process for recovering a dihydroxy compound from a fluid stream that results from the preparation of a polyester comprising the steps of: (a) providing a reactor having an internal volume wherein at least a portion of the internal volume is occupied by a reaction mixture comprising at least one dicarboxylic acid or ester thereof and at least one dihydroxy compound; (b) esterifying or transesterifying the at least one dicarboxylic acid or ester thereof with the at least one dihydroxy compound in the reactor to thereby produce: (i) an esterification product or transesterification product; and (ii) a fluid stream comprising the at least one dihydroxy compound; and (c) subjecting the fluid stream resulting from the esterification or transesterification reaction of step (b) to an adsorption system to selectively recover the dihydroxy compound.
In a second aspect, the present invention provides a process for recovering a dihydroxy compound from a fluid stream that result from the preparation of a polyester polymer comprising the steps of: (a) providing a reactor having an internal volume wherein at least a portion of the internal volume is occupied by a polyester monomer; (b) polycondensing the polyester monomer to produce a polyester polymer and fluid stream comprising the dihydroxy compound; and (c) subjecting the fluid stream resulting from the polycondensation reaction to an adsorption system to selectively recover the dihydroxy compound.
In a third aspect, the present invention provides a process for recovering a dihydroxy compound from a fluid stream that results from the preparation of a polyester polymer comprising the steps of: (a) providing a first reactor having a first internal volume wherein at least a portion of the first internal volume is occupied by a reaction mixture comprising at least one dicarboxylic acid component and at least one dihydroxy compound component; (b) esterifying or transesterifying the at least one dicarboxylic acid component with the at least one dihydroxy compound component to produce: (i) an esterification product or transesterification product; and (ii) a first fluid stream comprising the dihydroxy compound; (c) providing a second reactor in fluid communication with the first reactor having a second internal volume wherein at least a portion of the second internal volume is occupied by the esterification or transesterification product of step (b); (d) polycondensing the esterification or transesterification product of step (c) to produce a polyester polymer and a second fluid stream comprising the dihydroxy compound; and (e) subjecting the first fluid stream from step (b) and the second fluid stream from step (d) to an adsorption system to selectively recover the dihydroxy compound.
In still another aspect, the present invention further provides a process for recovering a dihydroxy compound from a fluid stream that result from the preparation of a polyester comprising the steps of: (a) providing a reactor having an internal volume wherein at least a portion of the internal volume is occupied by a reaction mixture comprising at least one dicarboxylic acid or ester thereof and at least one dihydroxy compound; (b) esterifying or transesterifying the at least one dicarboxylic acid or ester thereof with the at least one dihydroxy compound in the reactor to thereby produce: (i) an esterification product or transesterification product; and (ii) a fluid stream comprising the at least one dihydroxy compound; and (c) in the absence of a water column, subjecting the fluids stream resulting from the esterification or transesterification reaction of step (b) to an adsorption system to selectively recover the dihydroxy compound.
Additional advantages and embodiments of the invention will be obvious from the description, or may be learned by practice of the invention. Further advantages of the invention will also be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. Thus, it is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory of certain embodiments of the invention and are not restrictive of the invention as claimed.